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Home , Ancylostoma ceylanicum, Balantidiasis, Blastocystosis, Capillariasis, Dientamoeba fragilis, Fasciolopsiasis

Parasitic organisms: (P), Potential pathogen (PP), Non-pathogen (NP) Parasitic Organisms

NEMATODESNematodes – roundworms – ROUNDWORMS Organism Description Epidemiology/ Pathogenicity Symptoms -Necator Found in tropical and subtropical Necator can only be transmitted through penetration of the Some are asymptomatic, though a heavy burden is climates, as well as in areas where skin, whereas Ancylostoma can be transmitted through the associated with , fever, , nausea, Soil-transmitted sanitation and are poor.1 skin and orally. , rash, and abdominal .2 occurs when individuals come Necator attaches to the intestinal mucosa and feeds on During the invasion stages, local skin irritation, elevated into contact with soil containing fecal mucosa and blood.2 ridges due to tunneling, and rash lesions are seen.3 (P) matter of infected hosts.2 Ancylostoma eggs pass from the host’s stool to soil. Larvae Ancylostoma and Necator are associated with iron can penetrate the skin, enter the lymphatics, and migrate to deficiency anemia.1,2 heart and .3 Soil-transmitted Common in Sub-Saharan Africa, South Ascaris eggs attach to the small intestinal mucosa. Larvae Most patients are asymptomatic or have only mild America, , and the Western Pacific. In migrate via the portal circulation into the pulmonary circuit, abdominal discomfort, nausea, dyspepsia, or loss of non-endemic areas, infection occurs in to the alveoli, causing a pneumonitis-like illness. They are appetite. Most common immigrants and travelers. coughed up and enter back into the GI tract, causing

infection obstructive symptoms.5 Complications include obstruction, , right

It is associated with poor personal upper quadrant pain, and biliary colic.4 (P) hygiene, crowding, poor sanitation, and places where human are used as Intestinal can mimic intestinal obstruction, fertilizer. bowel infarction, intussusception, and . Hepatic and pancreatic ascariasis can mimic biliary colic, acute Transmission is via the fecal-oral route.4 acalculous , hepatic abscess, acute , and . Appendicular ascariasis can mimic appendicular colic, appendicitis, appendicular gangrene. Gastric ascariasis can mimic pyloric obstruction.6 Capillaria philippinensis Fish-borne nematode Although rare in the US, it is more Ingested larvae reside in the human , where Diarrhea, anorexia, malaise, and vomiting.4 common in Asia ( and the the female deposits eggs, which then develop, causing (P) Philippines)4 autoinfection and hyperinfection.4 can mimic IBD and other causes of protein losing .6 Infection occurs from eating raw or undercooked fish containing larvae. Enterobius vermicularis Compared to other intestinal parasites, Eggs are deposited around the anus by the worm. Some are asymptomatic. the transmission of pinworm is limited Autoinfection occurs due to scratching the perineal area, The most common worm because their eggs are unable to survive then thumb-sucking or nail-biting. Pinworms reside in the Symptoms may include itching and irritation. Occasional infection in children ages in the environment. The main routes of intestine but can migrate to distant organs.4 migration of the worm to distant organs can cause 5-10 in the US infection are autoinfection from eggs or , , , and peritoneal larvae deposited on the anus, granulomas.4 (P) contamination from bed sheets, clothing, door handles, and inhalation of eggs from Enterobiasis can mimic and IBD.6

Pathogen (P), Potential pathogen (PP), Non-pathogen (NP) 1 Parasitic Organisms NEMATODES – ROUNDWORMS Organism Description Epidemiology/Transmission Pathogenicity Symptoms hands, bed mattresses, or dust. As a result, infections tend to be limited to families and individuals in close proximity, like nurseries and boarding schools.7

Spread by overcrowding and poor hygiene.

Strongyloides stercoralis Soil-transmitted Endemic to the tropics and temperate Infection occurs from skin penetration where the organism Most patients have subclinical or asymptomatic nematode subtropics where poor sanitation then travels systemically (blood, , GI tract).8 infections. They are commonly chronic and longstanding facilitates fecal contamination. Also found due to the autoinfective lifecycle.4 (P) in poorer areas of the US: Appalachian stercoralis is unique among nematodes mountain communities, Kentucky, and infections in because larvae passing in the feces can Irritation, edema, and urticaria at the site of skin rural Tennessee.1 give rise to a free-living generation of . The potential penetration.8 for autoinfection exists if larvae attain infectivity while in the Transmission is from contaminated soil.8 host.4 Diarrhea, , , anorexia.

Dry cough, tracheal irritation, recurrent asthma.8

Strongyloidiasis can mimic IBD and eosinophilic .6

Trichuris trichiura Whipworm Found in areas where is used A human host consumes eggs, sometimes in . Once the Mild infections are usually asymptomatic. Heavy worm as fertilizer. Found in the tropics and eggs are ingested, the larvae hatch in the small intestine. burden causes painful with mucus, , and Soil-transmitted places with poor sanitation. From there they migrate to the , where the blood (Trichuris syndrome). is nematode anterior ends lodge within the mucosa. This leads to cell also seen.9 Transmitted via the fecal-oral route.4 destruction and activation of the host , The third most common recruiting eosinophils, lymphocytes, and plasma cells. This Children develop anemia, growth roundworm in humans4 causes the typical symptoms of rectal bleeding and retardations, and impaired cognitive development.4 abdominal pain.9 (P) can mimic IBD, bacillary dysentery and acute intestinal amebiasis.6

Pathogen (P), Potential pathogen (PP), Non-pathogen (NP)2 2 Parasitic Organisms

CESTODESCestodes – tapeworms – TAPEWORMS Organism Description Epidemiology/Transmission Pathogenicity Symptoms Dipylidium caninum (or ) tapeworm Human infection is rare but can occur in ingest D. caninum eggs. Adult fleas are ingested by Most are asymptomatic. When present, symptoms include those who kiss or are licked by their and establish in the small intestine where the eggs develop , colic, and vomiting.11 (P) infected pets.10 into the adult tapeworm. The tapeworm sheds proglottids, which are found in the stool. Humans are infected by

accidental of infected dog or cat fleas.10 latum Fish tapeworm D. latum occurs in freshwater fish After ingestion, in humans the adult helminth can live up to Mostly asymptomatic, but can include throughout much of the northern 20 years in the small intestine. It adheres to the mucosa and nausea, vomiting, diarrhea, abdominal pain, and weight (P) hemisphere; intermediate hosts include can eliminate millions of eggs each day. Diagnosis is made loss.11 bears, pigs, , , foxes, and . by the demonstration of eggs or proglottids in the stool.12 Can cause megaloblastic anemia.6 Humans become infected after eating raw or undercooked fish.11 Rat tapeworm Human infection with H. diminuta is rare Once ingested, H. diminuta grows to adult form and sheds Infection is usually asymptomatic, though may cause with only a few hundred cases reported, eggs through the stool. It attaches to the mucosal surface of abdominal pain, diarrhea, and .14 (P) mainly in children. the intestine and grows to approximately 20-50 cm. in H. diminuta is prevalent worldwide in length.

temperate to tropical conditions with poor sanitation.13

H. diminuta infection requires an intermediate host (usually , but also ). Humans become infected by ingesting food contaminated with larvae, or by direct hand contact.14 Dwarf tapeworm H. nana is one of the most common H. nana eggs are immediately infective when passed through Symptoms include abdominal pain, diarrhea, anorexia, parasitic tapeworm infections worldwide, the stool and cannot last more than 10 days in the weight loss, malnutrition, and anemia.18 (P) found mainly in children. environment.

It does not require an intermediary host Once ingested, larvae penetrate intestinal villi and develop and can be transmitted human to human, into adults that measure 15-40 cm. in length. Eggs pass into though rodents can also carry H. nana.15 stool or can reside within the intestinal villi and cause continual autoinfection.17 It has fecal-oral transmission from food and water in areas of poor sanitation.16

Pathogen (P), Potential pathogen (PP), Non-pathogen (NP) 3 Parasitic Organisms CESTODESOrganism – TAPEWORMS Description Epidemiology/Transmission Pathogenicity Symptoms Taenia spp. Organism TapewormDescription ThisEpidemiology/Transmission tapeworm is found in people who Ingested parasite cystsPathogenicity reach the intestine and develop into The adult tapeworm stageSymptoms is relatively innocuous and does have traveled outside of the US where the adult tapeworms, releasing motile segments and/or eggs in not have human pathogenic effects. However, some Taenia spp. Tapeworm This tapeworm is found in people who Ingested parasite19 cysts reach the intestine and develop into The adult tapeworm stage is relatively innocuous and does (P) haveinfection traveled is endemic outside, or of in the Latin US whereAmerican the theadult stool. tapeworms, releasing motile segments and/or eggs in ’not have intermediate human pathogenic stages caneffects. develop However, in human some brains immigrants. Locally acquired infections 19 causing neurocysticercosis, a major cause of neurologic Taenia saginata (P) infection is endemic, or in Latin American the stool. species’ intermediate stages can develop in human brains immigrants.are rare but have Locally been acquired diagnosed infections in Los One adult tapeworm can expel a minimum of 100,000 eggs diseasecausing inneu developingrocysticercosis, countries. a major cause of neurologic Taenia solium areAngeles, rare but New have York, been Chicago, diagnosed and Oregon. in Los perOne day. adult The tapeworm enclosed can larvae expel penetrate a minimum the intestinalof 100,000 wall eggs disease in developing countries. Angeles, New York, Chicago, and Oregon. andper day. are transported The enclosed via larvae the bloods penetratetream the to intestinal various tissues wall can develop in other organs causing Infection occurs upon ingestion of raw or whereand are they transported undergo viamultiple the bloods developmenttream to variousstages to tissues intramuscular,Cysticercosis can ocular, develop subcutaneous, in other organs and causing spinal Infectionundercooked occurs meat. upon4 ingestion of raw or becomewhere they cysticerci. undergo20 multiple development stages to cystericoses.intramuscular,19 ocular, subcutaneous, and spinal undercooked meat.4 become cysticerci.20 cystericoses.19 can mimic IBS.6 Taeniasis can mimic IBS.6

TREMATODESTrematodes – flukes – FLUKES TrematodesOrganism – flukes Description Epidemiology/Transmission Pathogenicity Symptoms Clonorchis - Organism Liver flukesDescription ClonorchisEpidemiology/Transmi and Opisthorchis infectionssions Adult flukes attach to Pathogenicitybile ducts where they feed for as long Early infection is often asymptomatic.Symptoms Chronic infection is OpisthorcClonorchish -is spp. Liver flukes haveClonorchis been andreported Opisthorchis in many infection parts ofs east asAdult 10- flukes30 years, attach resulting to bile in ducts chronic where inflammation, they feed for epithelial as long associatedEarly infection with is cholangitis, often asymptomatic. obstructive Chro jaundice,nic infection biliary is Opisthorchis spp. Asia,have Thailand,been reported Laos, in , many parts and of east hyperplasia,as 10-30 years, fibrosis, resulting and ingranuloma. chronic inflammation,22 epithelial fibrosis,associated cholecystitis, with cholangitis, and . obstructive jaundice,24 biliary (P) 22 24 Japan.Asia, Thailand,21 Laos, Cambodia, and hyperplasia, fibrosis, and granuloma. fibrosis, cholecystitis, and cholangiocarcinoma. (P) 21 Japan.

These flukes live in freshwater and Both are classified as Group 1 carcinogens. Infection by these These flukes live in freshwater snails and Both are classified as Group 1 carcinogens. Infection by these fish. Humans are infected by eating raw parasites is frequently asymptomatic and rarely diagnosed fish. Humans are infected by eating raw parasites is frequently asymptomatic and rarely diagnosed or partially cooked, infected fish. during early exposure. Persistent infection is associated with or partially cooked, infected fish. during early exposure. Persistent infection is associated with parasite-associated cancer. The mechanism of this parasite-associated cancer. The mechanism23 of this transformation is yet to be fully defined.23 Fasciola spp.- -borne intestinal Largely confined to Asian countries, After ingestion, gastric juices aid the release of the worm. Light infections are often asymptomatic. Moderate to 25 buski ova fluke including .25 The worm migrates to the small intestine, and produces heavy infection causes abdominal pain, diarrhea, nausea, 26 eggs, which are passed in feces.26 vomiting, and fever. Extensive intestinal inflammation, F. buski is known as the Humans are infected by ingesting eggs erosions, ulceration, abscess, and hemorrhage are giant intestinal fluke, and adhering to the surface of edible water possible.26 is one of the largest .25 flukes to infect humans.25

F. hepatica is a .

(P) Heterophyes - Fish-borne intestinal These are mostly seen in Far East and Mechanical irritation is caused by movement of the worms Mucosal changes lead to nutrient , intestinal 27 27 Metagonimus ova fluke Asian countries.27 causing mucosal villous atrophy. Chemical permeability, and watery diarrhea.27 Abdominal pain, 27 excretory/secretory proteins acts as active antigens and weight loss, and anorexia are also seen.27 27 These flukes are exclusively fish-borne toxins, provoking a systemic immune response.27 and are contracted by humans by (P) and are contracted by humans by ingesting raw or improperly cooked freshwater or brackish fish. freshwater or brackish fish.

Pathogen (P), Potential pathogen (PP), Non-pathogen (NP) 4 Parasitic Organisms TREMATODES – FLUKES Organism Description Epidemiology/Transmission Pathogenicity Symptoms Paragonimus spp. Lung fluke There are roughly 9 species that cause After ingestion of infected crabs or crayfish, the fluke resides Patients are often asymptomatic after ingestion and during clinical disease in humans, but only in the small intestine and migrates through the intestinal the initial migration phase. Some patients may develop P. kellicotti is endemic to North America, wall into the peritoneal space and eventually into the pleural abdominal pain and diarrhea. After migration to the pleural (P) where it is found in streams and rivers in space.11 space, inflammatory pulmonary symptoms begin.11 the Mississippi River Basin, including the central United States west to the Rocky Typical features of pulmonary include Mountains.11 cough, hemoptysis, chest pain, and dyspnea.28

Infection is caused by ingestion of raw or undercooked crabs or crayfish.28 spp. Blood fluke This organism is prevalent in the tropics Humans acquire the infection by direct contact with water Schistosome egg deposition and fluke burden can occur in and subtropics where poor sanitation is sources containing infectious larvae. The larvae penetrate any ectopic site, giving rise to site-specific symptoms and S. mansoni, S. japonicum, common.30 skin and enter the circulation via the capillaries and disease. These include , abdominal pain, and S. mekongi cause lymphatics.30 diarrhea, , GI bleeding, and urinary obstructive intestinal disease29 S. mekongi is primarily limited to the symptoms.30 Mekong River Basin stretching from Laos S. haematobium causes to Cambodia.29 Intestinal can mimic and IBD. urinary disease Hepatic schistosomiasis can mimic alcoholic and liver .6 (P) Humans contract the infection via water sources.30

Pathogen (P), Potential pathogen (PP), Non-pathogen (NP) 5 Parasitic Organisms PROTOZOAProtozoa Organism Description Epidemiology/Transmission Pathogenicity Symptoms coli protozoan Balantidium is reported worldwide, but is Trophozoites inhabit the intestine, feeding on and Often asymptomatic, but in the acute form symptoms more prevalent in temperate and tropical other intestinal contents. In most cases, infections are may include mucus and blood in feces. In severe cases, (PP) regions. asymptomatic and the infected host shows no clinical signs, hemorrhages and perforation could occur. Chronic suggesting that this ciliate is an opportunistic parasite that infection may present with unspecific abdominal Human infections are related to poor could take advantage of the host’s weakened status caused disorders (diarrhea, abdominal pain), cramping rectal sanitation and drinking water contaminated by other infections or diseases. In such cases, the parasite pain, nausea, and vomiting.31 with human and (swine) feces.4 could invade the intestinal wall, causing the disease known as or balantidial dysentery.31 Balantidiasis can mimic traveler’s diarrhea, invasive amebiasis, bacterial dysentery and IBD.6 spp. Although there are 17 Blastocystis is one of the most common Blastocystis resides in the and , adheres to Blastocystis is often asymptomatic. When present, different Blastocystis parasites, affecting 1.5-30% of those in mucus’ outer layer, and uses certain bacteria as a nutritional symptoms include nausea, anorexia, abdominal pain, subtypes, subtypes 1-9 are industrialized countries and 30-76% in source. (30) Its pathogenicity is controversial.32 flatulence, acute/chronic diarrhea, constipation, anal the only subtypes found in developing countries.32,33 itching, fatigue, joint pain, and urticaria. humans. It is associated with higher microbial diversity, and may be Blastocystis transmission is via the fecal-oral regarded as a commensal organism.33 It is associated with (IBS), and Subtypes 1-4 make up route by ingesting contaminated food or is three times higher in patients with IBS-D.36 90%. water, exposure to daycare environments, Literature-based conclusions about disease associations and and exposure to domestic and wild subtype pathogenicity is conflicting, but evolving. can mimic acute viral , and Subtype 3 is most .34,35 traveler’s diarrhea.6 common. Various subtypes have different zoonotic Subtypes have geographic transmissions. distribution.

(PP) Non-pathogenic parasite C. mesnili is found in about 3.5% of the US C. mesnili lives in the cecum and colon, but is noninvasive Although C. mesnili is nonpathogenic, and causes no population.37 and nonpathogenic.37 symptoms, it often occurs with other parasitic (NP) infections.37 Transmission is fecal-oral via the ingestion of mature cysts from contaminated water or food. spp. Coccidian parasite Cryptosporidium is endemic to North, The parasite adheres to intestinal epithelial cells. The In immunocompetent patients, infection is self-limiting Central, and South America, Africa, and intestinal releases to incite an with 2 weeks of watery diarrhea. Other symptoms (P) . immune response and causes cell and villous include fever, nausea, vomiting, and abdominal pain. atrophy. Cryptosporidium has developed ways to slow this Symptoms can be cyclical.39,40 Infection is spread via the fecal-oral route protective mechanism; therefore, host immune competency and indirectly through contaminated water. determines pathogenicity.38 It can be life threatening in immunocompromised Cryptosporidium is a common cause of food patients.4,41 and water-borne outbreaks.4 Enteric can mimic malabsorption syndrome, , and viral diarrhea. Biliary cryptosporidiosis can mimic acute cholangitis.6

Pathogen (P), Potential pathogen (PP), Non-pathogen (NP) 6 Parasitic Organisms Organism Description Epidemiology/Transmission Pathogenicity Symptoms Food- and waterborne Cyclospora is endemic to Nepal, Haiti, Peru, Individuals with Cyclospora infection excrete unsporulated is marked by profuse, non-bloody, coccidian parasite and Guatemala, but it has been found as a oocysts in their feces. These oocysts require 7 to 15 days to watery diarrhea, anorexia, fatigue, weight loss, nausea, cause of traveler’s diarrhea worldwide. sporulate and become infectious to a susceptible host. flatulence, abdominal cramping, myalgias, vomiting, There have been many US outbreaks related When food or water contaminated with infectious oocysts is and low grade fever. (P) to imported fruits and vegetables.4,42 In the ingested by a susceptible host, the oocysts excyst and US, increased cases are reported during the sporozoites are released and infect epithelial cells of the Symptoms start approximately 7 days after ingestion. If spring and summer months. and .43 left untreated, it can last weeks to months, with remitting and relapsing symptoms.4 Transmission is fecal-oral via ingestion of contaminated water or food. Cyclosporiasis can mimic acute viral enteritis and traveler’s diarrhea.6 Cystoisospora spp. Coccidian parasite Cystoisospora is an uncommon human Cystoisospora releases sporozoites that penetrate the small Some Cystoisospora infections are asymptomatic. When intestinal parasite. It has a worldwide intestinal columnar epithelium.47 present, infections are usually mild and self-limiting, distribution. consisting of diarrhea and abdominal pain.45 Previously referred to as Isospora44 Cystoisospora is frequently found in tropical It can cause severe chronic diarrhea in and subtropical regions.45 immunocompromised AIDS patients. It has also been (P) reported to be a cause of traveler’s diarrhea in the Transmission is through the fecal-oral route normal host and can mimic giardiasis or

by the ingestion of contaminated water and cryptosporidiosis.48 food.46 Flagellate protozoan D. fragilis has a worldwide distribution, and The role of D. fragilis as a pathogen is controversial because Although many patients are asymptomatic, D. fragilis parasite is transmitted via the fecal-oral route. the trophozoites are not invasive and patients are has been associated with diarrhea, abdominal pain, commonly asymptomatic.4 nausea, weight loss, anorexia, and flatulence.4 (P) Transmission via helminth eggs (Ascaris, Enterobius) has also been postulated, but is Dientamebiasis can mimic eosinophilic and IBD.6 still being investigated. Entamoeba coli Non-pathogenic E. coli is cosmopolitan in distribution and E. coli lives inside the large intestine but never enters the The presence of E. coli is not cause to seek treatment has been postulated to occur in mucosa or sub-mucosal intestinal layers. and is harmless. However, when a patient is infected (NP) approximately 50% of the population.49 with this benign amoeba, introduction of other pathogenic organisms is possible and may cause Transmission is fecal-oral via the ingestion symptoms.37 of contaminated water or food.49 Entamoeba dispar Non-pathogenic amoeba It is speculated that this species is E. dispar is noninvasive and considered non-pathogenic.50 E. dispar infection is not associated with clinical responsible for most infections that were symptoms. E. dispar is morphologically previously considered to be E. histolytica. E. and genetically similar to dispar has a high worldwide .50 the virulent E. histolytica; therefore, other laboratory methods are necessary to Transmission is fecal-oral via the ingestion distinguish the two.50 of contaminated water or food.51

(NP)

Pathogen (P), Potential pathogen (PP), Non-pathogen (NP) 7 Parasitic Organisms PROTOZOAOrganism Description Epidemiology/Transmission Pathogenicity Symptoms Entamoeba hartmanniOrganism Non-pathogenicDescription amoeba E. hartmanniEpidemiology/Transmi has a worldwide distribution,ssion E. hartmanni is non-pathogenic.Pathogenicity53 E. hartmanni infectionSymptoms is not associated with clinical Entamoeba hartmanni Non -pathogenic amoeba E.but hartmanni is most common has a worldwide in developing distribution, E. hartmanni is non-pathogenic.53 E.sympto hartmannims. infection is not associated with clinical 53 E. hartmanni can be butcountries is most with common poor sanitation. in developing symptoms. E.distinguished hartmanni can from be the countries with poor sanitation.53 distinguishedvirulent E. histolytica from the by Transmission is fecal-oral via the ingestion virulentthe much E. smaller histolytica cyst by Transmissionof mature cysts is fecalfrom- contaminatedoral via the ingesti wateron or 52 52 thesize. much smaller cyst offood. mature cysts from contaminated water or size. 52 food.52 (NP ) (NP ) The leading parasitic cause E. histolytica has a worldwide distribution, Cysts are ingested and excystation occurs. Colonization Although many cases are asymptomatic, it is likely that 52 Entamoeba histolytica Theof mortality leading parasiticglobally, cause and E.but histolytica is most common has a worldwide in developing distribution, Cystsusually are happens ingeste din and the excystationlarge bowel, occurs. but the Colonization cecum is most Althoughmisdiagnosis many is thecases cause are asymptomati(failure to identic, itf yis E. likely that 53 ofthe mortality third most globally common,52 and butcountries is most with common poor sanitation. in developing usuallycommon. happens It penetrates in the largethe endothelium bowel, but the causing cecum ulceration. is most misdiagnosisdispar/hartmanni is the). cause (failure to identify E. theparasitic third infectionmost common in the countries with poor sanitation.53 common.Host factors It penetratesappear to promote the endothelium a more invasive, causing systemiculceration. dispar/hartmanni ). 4 parasiticUS. infection in the Hostdisease factors, leading appear to dysentery, to promote liver a more absc invasive,ess, systemic Symptoms of E. histolytica infection () US. 4 Transmission is fecal-oral via ingestion of diseasepleuropulmonary, leading to involvement, dysentery, liver and abs manycess, other systemic Symptomsinclude hemorrhagic of E. histolytica diarrhea, infection fatigue, (amoebiasis) nausea, fever, 53 55 Erythrophagocytosis has Transmissionmature cysts fromis fecal contaminated-oral via ingesti wateron ofor pleuropulmonarycomplications. involvement, and many other systemic includeweight loss.hemorrhagic diarrhea, fatigue, nausea, fever, 53 Erythrophagocytosisbeen used as a diagnostic has maturefood, or cystscontaminated from contaminated individuals. water or complications. 53 weight loss.55 beenindicator used of as invasi a diavgnostice E. food, or contaminated individuals.53 Intestinal amebiasis can mimic infectious diarrhea, IBD, 54 indicatorhistolytica of by invasi microscopy.ve E. Intesischemictinal colitis, amebiasis diverticulitis, can mimic AV infectious malformation. diarrhea, IBD, histolytica by microscopy.54 ischemicAmoeboma colitis, can diverticulitis,mimic colon carcinoma. AV malformation. Amebic ( P) Amoebomastrictures can can mimic mimic lymphogranuloma colon carcinoma. venereum Amebic (chlamydia) and malignancy. Hepatic amebiasis can (P) strictures can mimic lymphogranuloma venereum (chlamydiamimic pyogenic) and liver malignancy. abscess, Hepaticnecrotic amebiasis hepatoma can and 6 mimicechinococcal pyogenic cyst. , necrotic hepatoma and Entamoeba polecki Non-pathogenic amoeba Infection with E. polecki is rare, though its E. polecki is non-pathogenic. echinococcalE. polecki infection cyst.6 is not associated with clinical Entamoeba polecki Non -pathogenic amoeba Infectionprevalence wi andth E. distribution polecki is rare are, thoughoften its E. polecki is non-pathogenic. E.symptoms. polecki infection is not associated with clinical E. polecki can be prevalenceconfused with and those distribution of the other are often symptoms. 56,57 E.distinguished polecki can be from other confusedEntamoeba with species those. of the other distinguishedEntamoeba species from otherby Entamoeba species.56,57 Entamoebamicroscopy. speciesIt is the by only 56 microscopy.uninucleated It species. is the only E. polecki, much like all Entamoeba species, uninucleatedE. polecki comprises species. four56 E.is transmittedpolecki, much through like all the Entamoeba fecal-oral species, route E.subtypes, polecki comprises all of which four are isby transmitted the ingestion through of contaminated the fecal-oral food route or 56 56 subtypes,found in humans. all of which are bywater the. ingestion of contaminated food or found in humans.56 water.56 (NP) Endolimax nana (NP)Non-pathogenic protozoa E. nana has a global distribution. E. nana inhabits the colon and has been found in the Endolimax is an indicator of fecal contamination, which 58 Endolimax nana Non -pathogenic protozoa E. nana has a global distribution. E.. nana inhabits E. nana the feeds colon on and bacteria has been and foundis non -ininvasive. the Endolimaxoften entails is anco- indicatorinfection ofby fecal other contamination, organisms capable which (N P) E. nana is transmitted through the fecal-oral appendix. E. nana feeds on bacteria and is non-invasive.58 oftenof causing entails diarrhea. co-infection There by are other rare organismscases of associati capableons E.route nana through is transmitted ingestion through of contaminat the fecaled-oral ofwith causing urticaria, diarrhea. polyarthritis, There are and rare diarrhea. cases of However, associati ons (NP) 58 58 routefood or through water. ingestion of contaminated withthere urticaria, is too little polyarthritis, evidence to and support diarrhea. pathogenicity. However, food or water.58 there is too little evidence to support pathogenicity.58

Pathogen (P), Potential pathogen (PP), Non-pathogen (NP) 8 Parasitic Organisms

PROTOZOA Organism Description Epidemiology/Transmission Pathogenicity Symptoms Flagellate protozoa Giardia has a worldwide distribution. In Giardia (via secretory and excretory proteases) may alter the Giardia is a leading cause of diarrhea worldwide. Some the US, it is more frequently reported in structure and composition of human intestinal microbiota cases may be asymptomatic; when present symptoms (P) children aged 1-9.59 biofilms. Bacteria from these dysbiotic microbiota in turn include diarrhea, bloating, malabsorption, nausea, can cause epithelial and intestinal abnormalities after the vomiting, and abdominal cramping. Infections are Giardia is transmitted through the fecal- enteropathogen has been cleared.60 normally self-limiting, but chronic diarrhea may occur oral route by the ingestion of in children.59 contaminated water and food.59 It is emerging as a prominent precursor to post- infectious irritable bowel syndrome and a variety of chronic extra-intestinal disturbances, such as reactive arthritis and chronic fatigue.60 Acute giardiasis can mimic acute viral enteritis, bacillary dysentery, acute intestinal amebiasis and IBD.6 Iodamoeba butschlii Non-pathogenic amoeba Iodamoeba has a worldwide distribution. Iodamoeba is usually found in the large intestine and are Iodamoeba is not associated with symptoms. However, Humans have a low prevalence of non-invasive.37 it is an indicator of fecal contamination, which often Iodamoeba gets its name from its Iodamoeba butschili. entails co-infection by other organisms capable of appearance when stained with causing diarrhea.37 iodine.37 Transmission is through the fecal-oral route by the ingestion of contaminated (NP) water and food.37 Trichomonads- Flagellate parasite Trichomonads have worldwide P. hominis, R. intestinalis, and E. hominis are considered Trichomonads in the stool are not related to Pentatrichomonas distribution. non-pathogenic commensals found in the cecum and gastrointestinal illness.37 Trichomonas tenax is usually colon.37 Pentatrichomonas hominis found in oral/periodontal E. hominis, P. hominis, and R. intestinalis The presence of trichomonad trophozoites in the stool infections and cannot survive are transmitted via the fecal-oral route can be an indicator of fecal contamination, and Enteromonis hominis intestinal passage. by the ingestion of contaminated water, therefore doesn’t rule out other infections as a cause of food, and .37 symptoms.37 intestinalis Pentatrichomonas hominis (also known as Trichomonas hominis) will not survive in the oral cavity or genitourinary tract. It is considered a non-pathogenic parasite.37

Trichomonas vaginalis is confined to the urogenital system. Among trichomonads, there is a habitat restriction: each can survive only in its site-specific location.37

(NP)

Pathogen (P), Potential pathogen (PP), Non-pathogen (NP) 9 Parasitic Organisms TREATMENT RESOURCES: The decision to treat parasitic organisms should be based on the patient’s clinical presentation. The following resources provide valuable insight into the clinical management of parasitic infections: • Center for Disease Control – monographs on individual parasites and • CDC hotline for healthcare providers with questions regarding parasites: treatment protocols: https://www.cdc.gov/parasites/ - Parasitic Diseases Hotline (M-F; 8am-4pm EST) 404-718-4745 • Sanford Guide - infectious disease treatment guidelines: - Emergency, after-hours hotline 770-488-7100 https://www.sanfordguide.com/ • Mayo Clinic – conditions search engine: https://www.mayoclinic.org/ • PubMed – literature search engine: https://www.ncbi.nlm.nih.gov/pubmed/ REFERENCES 1. McKenna ML, McAtee S, Bryan PE, et al. Human intestinal parasite burden and poor sanitation in rural alabama. The American 21. 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